Previous devices only measured pressure changes which occur in the human sphincters or only measured electrical changes in the cardiac region.
U.S. Pat. No. 3,480,003 is a pressure sensing apparatus for sensing esophogeal mobility around the sphincter region.
U.S. Pat. No. 3,939,823 shows an esophogeal transducer for measuring esophogeal contractions. This transducer is of a singular, circular fashion placed upon a catheter.
U.S. Pat. No. 4,168,703 discloses a tool for diagnosing a gastro-esophogeal reflex condition whereby the pressure at selected locations along the gastro-esophogeal tract in the body may be measured without disturbing the relative position of the device.
U.S. Pat. No. 4,706,688 relates to a cardiac device which is inserted into the gastro-esophogeal junction and comprises an elongated conduit having a series of electrodes for sensing or recording electrical signals of the cardiac region.
U.S. Pat. No. 4,304,239 shows an esophogeal probe with a pair of conductive electrodes being connected to the distal end of the probe's shaft to make improved contact with the patient's body on the esophagus to sense ECG waves.
U.S. Pat. No. 3,734,094 describes a multipurpose esophogeal instrument which is capable of withdrawing fluids and monitoring the heart simultaneously or in succession.
U.S. Pat. No. Re. 31,377 shows an esophogeal probe incorporating the capability to detect ECG waveforms, heart sounds, and to measure body core temperature.
Two other devices which record lower esophogeal sphincter pressure are the side-hole manometry and the Dent sleeve device.